Variable Allocation using @"SegmentName"

Sometimes it is useful to have the variable directly allocated in a named segment instead of using a #pragma. The following listing is an example of how to do this.

Listing: Allocation of variables in named segments

#pragma DATA_SEG __SHORT_SEG tiny #pragma DATA_SEG not_tiny 
#pragma DATA_SEG __SHORT_SEG tiny_b 
#pragma DATA_SEG DEFAULT 
int i@"tiny"; 
int j@"not_tiny"; 
int k@"tiny_b";

So with some pragmas in a common header file and with another definition for the macro, it is possible to allocate variables depending on a macro.

Declaration = <TypeSpec> <Declarator> [@"<Section>"][=<Initializer>];

Variables declared and defined with the @"section" syntax behave exactly like variables declared after their respective pragmas.

<TypeSpec> is the type specifier, e.g., int or char
<Declarator> is the identifier of your global object, e.g., i, glob
<Section> is the section name. Define it in the link parameter file as well (e.g., MyDataSection).
<Initializer> is the value to which the global variable is initialized.

The section name used has to be known at the declaration time by a previous section pragma.

Listing: Examples of section pragmas

#pragma DATA_SEC __SHORT_SEG MY_SHORT_DATA_SEC #pragma DATA_SEC              MY_DATA_SEC 
#pragma CONST_SEC             MY_CONST_SEC 
#pragma DATA_SEC   DEFAULT       // not necessary, 
                                 // but good practice 
#pragma CONST_SEC  DEFAULT       // not necessary, 
                                 // but good practice 
int short_var @"MY_SHORT_DATA_SEC"; // OK, accesses are 
                                        // short 
int ext_var @"MY_DATA_SEC" = 10;        // OK, goes into 
                                        // MY_DATA_SECT 
int def_var;  / OK, goes into DEFAULT_RAM 
const int cst_var @"MY_CONST_SEC" = 10; // OK, goes into 
                                        // MY_CONST_SECT

Listing: Corresponding Link Parameter File Settings (prm-file)

SECTIONS     MY_ZRAM  = READ_WRITE 0x00F0 TO 0x00FF; 
    MY_RAM   = READ_WRITE 0x0100 TO 0x01FF; 
    MY_ROM   = READ_ONLY  0x2000 TO 0xFEFF; 
    MY_STACK = READ_WRITE 0x0200 TO 0x03FF; 
END 
PLACEMENT 
    MY_CONST_SEC,DEFAULT_ROM INTO MY_ROM; 
    MY_SHORT_DATA_SEC        INTO MY_ZRAM; 
    MY_DATA_SEC, DEFAULT_RAM INTO MY_RAM; 
    SSTACK                   INTO MY_STACK 
END